1. Field of the Invention
The present invention generally relates to a radio frequency identification (RFID) chip, and more particularly, to an RFID chip using CMOS technology.
2. Description of Related Arts
In goods-related or services-related industries, it is necessary to inventory the item stock every while. Conventionally, manual labors have been employed to count the items located on the shelf, and those are otherwise located in the store or warehouse for a long time. For the purpose of easing off such time-consuming and labor-intensive jobs, a technology known as radio frequency identification (RFID) is provided to have the ability to monitor the items that are located within a particular range.
Based upon the RFID technology, RFID chips are affixed to each item to be monitored. The presence of the RFID chip, and therefore the item to which the chip is affixed, may be checked and monitored by devices known as RF readers. The RF reader may monitor the existence and location of the items having chips affixed thereto through wireless interrogations. Typically, each chip has a unique identification number that the RF reader uses to identify the particular chip and item. To efficiently avoid collisions between signals transmitted by the RFID chips, the interrogation protocol, such as the binary traversal protocol, may be employed to exchange the signals between the RF readers and the RFID chips. Examples of such binary traversal protocol is described in U.S. Patent Application Publication Nos. 20020167405A1, 20020152044A1, 20020149483A1, 20020149482A1, 20020149481A1, 20020149480A1, and 20020149416A1, all of which are incorporated herein by reference.
Because a great many items may need to be monitored, many chips may be required to track the items. Hence, the cost of each RFID chip needs to be minimized. However, current available RFID chips configured with external batteries are expensive. For the foregoing reasons, there is a need for passive RFID chips with implementation without external batteries, which are inexpensive and small while the read range thereof is satisfactory.